Jim Smart
April 1, 2009
Here's the Heidts coilover rear suspension setup installed and ready to go in our '68 fastback. Carrying PN RM-101, it's also available with a 9-inch axle housing under PN RM-101-H. We were able to do the installation in about two days, not including the three pieces that needed to be welded to the axle housing. The rest of the system is a true bolt-in installation. It does require holes to be drilled for installation of the various brackets. Note that the tailpipes have been removed; they will be reinstalled at a muffler shop to fit around the Panhard rod and coilovers.

There's no question that leaf-spring vintage Mustangs can be made to handle pretty well. With updates such as mid-eye leaf springs, performance shocks, and a rear antisway bar, cornering prowess can be raised to a respectable level.

But when you make the move to a three- or four-link system, which eliminates the leaf springs and adds a Panhard bar or a Watt's link along with coilover shocks, you've clearly moved into a different realm of suspension design and technology.

While there are several rear coilover suspension systems on the market for '65-'70 Mustangs and all have their unique design elements, two things they all offer are ride-height adjustability and better ride quality. There's no getting around the fact that a coilover suspension is going to improve the ride quality over a 40-year-old leaf-spring suspension. That's mainly due to the fact that to get a similar effect on handling improvement, the springs in a coilover system don't have to be as stiff as they do with leaf springs.

To quickly examine various designs on the market, you'll find the main players have a three-link with a torque arm as the third link; those setups usually include a Watt's link. Another design is a triangulated four-link that designers feel will work well without a Panhard bar or a Watt's link. A third school of thought is the system we're showing here. Offered by Heidts Hot Rod Shop, this arrangement is a straight four-link that also uses a Panhard bar. We stopped in at Reenmachine and watched our friend Pete Waydo install it on a customer's '68 fastback.

All three designs have merit and it's pretty much a matter of personal preference. In any case, a coilover design is worlds beyond what a leaf-spring setup offers. And we're sure many vintage Mustang owners will want to consider the previously mentioned attributes of better ride quality and the option to adjust ride height.